Genetic diversity and maternal ancestry line relationships amongst a sample of 96 Cleveland Bay horses were investigated using a 479bp length of mitochondrial D-loop sequence. The analysis yielded at total of 11 haplotypes with 27 variable positions, all of which have been described in previous equine mitochondrial DNA d-loop studies. Four main haplotype clusters were present in the Cleveland Bay breed describing 89% of the total sample. This suggests that only four principal maternal ancestry lines exist in the present-day global Cleveland Bay population. Comparison of these sequences with other domestic horse haplotypes shows a close association of the Cleveland Bay horse with Northern European (Clade C), Iberian (Clade A) and North African (Clade B) horse breeds. This indicates that the Cleveland Bay horse may not have evolved exclusively from the now extinct Chapman horse, as previous work as suggested. The Cleveland Bay horse re-mains one of only fivedomestic horse breeds classified as Critical on the Rare Breeds Survival Trust (UK) Watchlist and our results provide important information on the origins of this breed and represent a valuable tool for conservation purpos-es.

中文翻译：

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濒危克利夫兰湾马的线粒体D-环序列变异和母系

利用线粒体D-loop序列的479bp长度，对96名克利夫兰湾马的样本中的遗传多样性和母系关系进行了研究。分析产生了总共11种单倍型，具有27个可变位置，所有这些均已在先前的马线粒体DNA d环研究中进行了描述。克利夫兰湾品种中存在四个主要的单倍体簇，占总样品的89％。这表明在当今的全球克利夫兰湾人口中仅存在四个主要的母系血统。这些序列与其他家养马单倍型的比较显示，克利夫兰湾马与北欧（Cade），伊比利亚（Acade）和北非（B）马品种密切相关。这表明，克利夫兰湾赛马可能并不是像现在建议的那样，从已经灭绝的查普曼赛马中专门进化而来。克利夫兰湾的马仍然是被归类为“稀有动物生存信托（英国）监视中的重要动物”的仅有的五个国内马品种之一，我们的研究结果提供了有关该品种起源的重要信息，并代表了保护目的的宝贵工具。